1. Field of the Invention
The present invention relates generally to medical apparatus and methods and more particularly to devices and methods for removal of unwanted tissue such as thrombus, atheroma, fluid, polyps, cysts or other obstructive matter from body lumens, such as blood vessels, ureters, bile ducts or fallopian tubes.
Currently, there are many clinical approaches to removing unwanted material, many of which are performed surgically, wherein the treatment site is accessed directly through a surgical incision.
In recent years, a variety of catheter devices have been developed for use in intraluminal and intravascular procedures for fragmentation and removal of obstructive matter, such as blood clots, thrombus, atheroma, and the like, from blood vessels. More recently, devices that can be inserted percutaneously through a puncture in the skin have been developed to make the procedures less invasive. For example, a catheter device is inserted into a blood vessel at an access site located some distance away from the intended treatment site, and is then advanced through the vessel lumen until the treatment site is reached. In most instances this approach is performed “over-the-wire,” a technique that requires the physician to first place a guidewire device into the vessel lumen over which a larger catheter device can be tracked.
These techniques may employ various devices to fragment the unwanted clot or tissue from blood vessels such as rotating baskets or impellers as described in U.S. Pat. Nos. 5,766,191 and 5,569,275, cutters as described in U.S. Pat. No. 5,501,694, and high pressure fluid infusion to create a Venturi effect as described in U.S. Pat. No. 5,795,322. Other devices rely on the principles of the Archimedes-type screw, such as a one-piece solid machined screw to break up and/or remove clot.
In many instances, the luminal treatment techniques include infusing the vessel or treatment site with fluid (saline or a thrombolytic agent) to assist in breaking up the clot or tissue into a particle size that can then be aspirated through a lumen of the treatment device or using a secondary catheter hooked up to a source of vacuum/suction. Depending on the method of fragmentation and the consistency of the clot or tissue, the particle size can vary. If the material is not thoroughly fragmented, the larger particles can build up in the catheter and block the aspiration lumen.
While these catheters and techniques have been fairly successful, there is a need for improved devices for more efficiently evacuating fragmented material from the vessel or body lumen in order to overcome the difficulties of continued fluid infusion and material build up that blocks the aspiration lumen. Furthermore, it would be desirable to have devices that allowed aspiration of larger particles of fragmented material, thereby reducing procedure time. Preferably, such improved devices will have a low profile to enable percutaneous use, and will be flexible and torqueable to enable their use in tortuous lumens. Furthermore, such devices will preferably be designed to be placed over a guidewire and will be structured to mechanically translate and transport the fragmented material by directly pumping it through the catheter shaft. Optionally, the devices should include mechanisms for infusing materials, such as thrombolytic and other therapeutic agents, as well as disrupting the occlusive materials.
At least some of these objectives will be met by the design and use of the present invention.
2. Description of the Background Art
U.S. Pat. No. 5,556,408 describes an atherectomy cutter employing a vacuum source for removal of loose stenotic material and other debris from a vessel. Removal of thrombus by a rotating core wire on a drive shaft is described in U.S. Pat. No. 5,695,507 and fragmentation and removal of tissue using high pressure liquid is described in U.S. Pat. No. 5,795,322. U.S. Pat. No. 4,923,462 describes a coiled wire coated with Teflon and used as a drive shaft to rotate a catheter. Furthermore, U.S. Pat. No. 5,334,211 describes a coiled guidewire used to stabilize an atherectomy device. Patents describing atherectomy catheters with rotating helical pumping elements in U.S. Pat. Nos. 4,732,154; 4,886,490; 4,883,458; 4,979,939; 5,041,082; 5,135,531; 5,334,211; 5,443,443; and 5,653,696. A rotary thrombectomy catheter having an inner helical blade is commercially available under the tradename Straub Rotarex® from Straub Medical AG, as described in a brochure with a copyright of August 1999. Use and construction of the Straub Rotarex® also appears to be described in Schmitt et al. (1999) Cardiovasc. Intervent. Radiol. 22: 504-509 and in U.S. Pat. Nos. 5,876,414 and 5,873,882. Other patents of interest include U.S. Pat. Nos. 4,737,153; 4,966,604; 5,047,040; 5,180,376; 5,226,909; 5,462,529; 5,501,694; 5,569,275; 5,630,806; 5,766,191, 5,843,031; 5,911,734; 5,947,940; and 5,972,019; as well as published PCT applications WO 99/56801; WO 99/56638; and WO 98/38929. Motor drive units for catheters and other devices are described in U.S. Pat. Nos. 4,771,774 and 5,485,042.